Enteric fever caused by members of the genus Salmonella, including typhoid and paratyphoid fevers, continues to constitute a significant disease and mortality burden among populations in developing countries (Lancet 2005; 366:749-762) and represents a notable risk for travelers (Lancet Infect Dis. 2005; 5(10):623-628). Incidences of enteric fever caused by Salmonella enterica serovars Typhi and Paratyphi A (S. Typhi and S. Paratyphi A) are on the rise due to the emergence and spread of antibiotic resistant variants (Lancet Infect Dis. 2005 5(10):623-8). Although the clinical disease caused by S. Paratyphi A is overall somewhat milder than that due to S. Typhi, the former can nevertheless result in full-blown enteric fever with an assortment of complications and, if untreated or improperly treated, can result in death. A need exists for vaccines that are safe and effective in combating Salmonella infections.